Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.30	13.473%	$161.4721	$161.47	$161.45	$161.50
Purchase #2	$93.58	6.103%	$99.2912	$99.29	$99.30	$99.30
Purchase #3	$155.72	4.363%	$162.5141	$162.51	$162.50	$162.50
Purchase #4	$232.90	12.240%	$261.407	$261.41	$261.40	$261.40
Purchase #5	$33.87	11.115%	$37.6347	$37.63	$37.65	$37.60
Purchase #6	$219.48	4.749%	$229.9031	$229.90	$229.90	$229.90
Purchase #7	$185.88	10.133%	$204.7152	$204.72	$204.70	$204.70
7 purchase totals =	$1,063.73		$1,156.9374	$1,156.93	$1,156.90	$1,156.90